High speed circuit breaker



April 14, 1936' p w FORSBERG 2,037,570

HIGH SPEED CIRCUIT BREAKER Filed Feb. 1, 1955 '//I/I/'I/III/IIII//IIIIII] I Ihverfi'tor": peter WFonsberg,

LA r-ii zttorneg current.

Patented Apr. 14, 1936 UNITED srArs EFF-ICE General Electric Company,

New York a corporation of Application February 1, 1935, Seriai No. 4,51;

11 Claims.

moving parts and to eliminate so far as possible the necessity for heavybiasing springs. At the same time a suflicient closing bias must beprovided to resist the magnetic forces which tend to open theinterrupter contacts upon the flow of heavy currents therethrough.Satisfactory protection of an electric circuit subject to various typesof overloads requires that the protec tive device shall not only bequickly responsive to the value of current, so as to protect the circuitagainst a current which increases slowly to an abnormal value, but alsomust be quickly responsive to the rate of change of current so as toprotect the circuit against a suddent rush of Various devices haveheretofore been proposed for providing high speed circuit interruptionin response to abnormal conditions. Sat-' isfactory operation of suchdevices, however, in response both to steady currents of abnormal valueand to a sudden increase in current has required the use of auxiliarytripping relays or the partial sacrifice of high speed operation due tocumbersome mechanical expedients and the necessity for relatively strongbiasing means. Ac cordingly, it is a further object of my invention toprovide a high speed circuit breaker in which the closing bias appliedto the interrupter contacts depends upon the value of the normal currentcarried thereby and which is quickly oper able to interrupt the circuitin response either to a sudden rush of current or to an abnormal steadycurrent.

In accordance with one embodiment of my invention, the movable contactof a circuit breaker is carried on a movable supporting conductor aportion of which forms a side of a conductorloop disposed in a magneticfield the strength of which varies as the current through the circuitbreaker. When a substantially steady current flows through the circuitbreaker, the electrodynamic reaction between the current in the movableconductor and the magnetic field urges the conductor in a predetermineddirection and upon the occurrence of a predetermined rate of increase inthe current, a circulating current is induced in the conductor-loop bythe increase of flux therethrough to cause a reversal of current in theside thereof formed by the movable con ductor, the electrodynamicreaction with the magnetic field then moving the conductor in anopposite direction. More specifically, the movable contact of thecircuit breaker is carried by a supporting conductor comprising a pairof hinged arms arranged in endwise relation to form a toggle, one of thearms being pivoted intermediate its ends. The supporting conductor isdisposed in the magnetic field-with a portion of the conductor forming aside of a conductor-loop. Spring means are arranged normally to lock thetoggle arms in endwise relation and lightly to bias the contact tocircuit closing position. Upon the flow of normal relatively steadycurrents through the circuit breaker, the electrodynamic reactionsbetween the arms and the magnetic field are such as to increase the biason the circuit breaker contacts. Upon the occurrence of an abnormalsubstantially steady current, the electrodynamic reactions serve tobreak the toggle and open the circuit breaker contacts, while upon theoccurrence of a sudden increase in current, the electrodynamic reactionsmove the supporting conductor about its pivot to open the circuitbreaker contacts.

For a more complete understanding of my invention, reference should nowbe had to the drawing in which Fig. 1 is an elevational view partly insection, illustrating diagrammatically a circuit breaker embodying theprinciples of my invention; Fig. 2 is a sectional view taken along line2-2 of Fig. 1; Fig. 3 illustrates diagrammatically a preferred form ofcircuit breaker embodying my invention; Fig. illustrates a suitablecontrol circuit for manually tripping and resetting the circuit breakershown in Fig. 3, and Figs. 5 to 9 inclusive illustrate diagrammaticallyvarious operating positions of the circuit breaker shown in Fig. 3.

Referring to Figs. 1 and 2, the circuit breaker comprises a pair ofrelatively movable contacts in and i i disposed in a suitable arc chutel2, the movable contact it! being carried by a movable conductor memberl3 pivotally supported on a pin l4 and biased to circuit closingposition by a spring 95. The fixed contact II is connected in seriescircuit relation with a magnetic blow out coil 86 arranged to furnish a.suitable blow= out flux in a well-understood manner. In addition, theblow-out coil l5 serves to establish a magnetic flux through a magneticcircuit comprising the core member H, the opposed pole pieces 99 and i9and the air-gap 2d. Connected to the pivot pin i4 is a fixed conductor2i which cooperates with the movable conductor member 33 and a flexibleconductor 22 to form a conductor-loop disposed in the air-gap 2c andenclosing a portion of the flux therethrough.

With normal steady current flowing in the circuit to be controlled,represented by the line conductors 23 and 2d, the line current willdivide through the fixed conductor 29 and the movable conductor 6 3 asindicated by the solid arrows (Fig. 1), and the coil 58 will beenergized to establish a magnetic field which extends across the airgap253 in the direction indicated by the conventional symbols N and S (Fig.2) on pole pieces l9 and i8 respectively. Under these conditions theelectrodynamic reaction between the current in v the arm is and themagnetic field will tend to as indicated by the broken arrows (Fig. 1).

move the lower part of the arm in a clockwise direction about the pivotM whereby a contact pressure which increases approximately as the squareof the current is obtained without the use of a heavy biasing spring.

"Upon the occurrence of a sudden rush of current through the contacts 10and H and the blow-out coil iii, there will be a corresponding increasein the flux enclosed by the conductor-loop consisting of a portion of tharm l3, the fixed conductor 2! and the flexible conductor 22. Thissudden increase of flux through the loop will causean induced current toflow therein in a direction tending to oppose the increase of flux Ifthe rate of increase of current is sufilciently high, this inducedcurrent will cause the current in the lower part of the movable memberl3 to reverse and flow downwardly instead of upwardly, theelectrodynamic reaction of this reverse current with the magnetic fieldimmediately causing the pivoted conductor member I3 to move in acounterclockwise direction to open the contacts. It will be apparentthat the arrangement provided assures a very light high speed circuitbreaker which will trip on a. predetermined rate of change of currentand in which suitably high contact pressures are obtained without resortto heavy biasing springs.

The circuit breaker illustrated in Figs. 1 and 2 will not, however, tripon relatively steady abnorma] currents and while any suitable means maybe employed for accomplishing overload trip, the circuit breakerillustrated in Fig. 3 represents a preferred embodiment of my inventionwhich will trip on either substantially steady abnormal currents or inresponse to a predetermined rate of change of current. 1

Referring now to Figs. 3to 9, in this embodiment of my invention asecond conductor member I3 is interposed between the contact In and thearm I3, the arms I3 and I3 being arranged in endwise relation and hingedtogether at 25 to form a toggle. An overcenter spring .26 having one endfastened to the arm 13' at 21- and the other end fastened to a pin 28 ona. movable carrier 29 serves to lock the toggle arms-13 and i3 instraight line relationsand to bias the contact ill to circuit closingposition. It will be observed that the line of action of the spring 26is such as to exert a relatively weak biasing force on the contact I0and a. relatively strong locking force on the toggle arms. The movablecarrier 29 is plvotally supported on the pin H by means of an arm 30 andcarries a pin 3| which, to-- gether with the spring supporting pin 28,coopcrates with a finger 32, insulatedly mounted on the lower end of thearm 13, to manually trip and reset the circuit breaker in a manner to bemore fully described later. A pair of stop members 33 and 3311 areprovided for engaging the arms i3 and i3 respectively to limit themovement thereof when the circuit breaker is operated.

When normal current flows in the circuit to be controlled the currentdivides through the movable arm is and the fixed conductor 2! in thesame manner as set forth in connection with the circuit breaker shown inFig. l and flows through the conductor arm i3',,the contacts l0 and Hand the blow-out coil i6, thereby setting up a magnetic field betweenthe pole pieces l8 and I9. Under these conditions the electrodynamicreaction tends to move the arms l3 and I 3' to the left as viewed inFig. 3. The portion of arm l3, however, which is arranged in themagnetic field to react therewith is considerably greater than theportion of the am It so arranged, so that the reaction on the arm 13 isstronger than the reaction on the arm l3, and accordingly the arms l 3and l 3 tend to move together in a clockwise direction about the pin 14whereby an additional closing bias is exerted on the contacts, thespring 25 serving to maintain the toggle arms I3 and 13 in straight linerelation.

Upon the occurrence of a substantially steady but abnormal current how,the electrodynamic force exerted on the arms 13 and I3 becomessuflicient to overcome the locking force of the spring 26 and break thetoggle joint. As soon as the spring pressure is overcome the arms 13 and13' move quickly to the, position shown in Fig. 6. interrupting thecircuit. It will be observed that when the arms l3 and I3 move about thehinge 25, the spring 26 is carried overcenter and in the position shownin Fig. 6 is effective to latch the circuit breaker in open circuitposition.

The circuit breaker is also adapted for high speed operation in responseto a sudden rush of current. Upon the occurrence of a sudden increase inthe current, a circulating current will be induced in the conductor-loopin the manner described in connection with Fig. 1 and the electrodynamicforces will then tend to move the arm I 3 to the right, as viewed inFig. 3, and to move the arm l3 to the left, whereupon the arms will moveabout the pivot point 14 in a counterclockwise direction to the positionshown in Fig. 5, thereby interrupting the circuit. In this position ofthe circuit ,breaker the spring 28 is carried overcenter relative to thepivot II, but not relative to the hinge 25, and therefore the spring 26in this position serves to maintain the toggle arms in straight linerelation and also to latch the circuit breaker in open circuit position.

Manual tripping and resetting of the circuit breaker may be accomplishedby moving the carrier 29 about the pivot point I. Although any suitablemeans may be employed for obtaining the desired movement of the carrier29, I have shown in Fig. 4, a preferred arrangement for manuallytripping and resetting the circuit breaker. As shown in Fig. 4, thecarrier supporting arm 30 provided with a latch 34 arranged to cooperatewith a pivoted finger 35 to hold the carrier 29' in its reset positionagainst the force exerted by an operating spring fastened to a finger 31on the carrier. The pivoted finger 35 is normally held in latchingposition by a tripping coil 35 against the force exerted by a trippingspring 49. Connected to the finger 31 on the carrier 29 by means of apin and slot connection 4!, is an operating rod 42, the other end of therod 42 being connected to the core 43 of a solenoid having an operatingwinding 44. In order selectively to energize the operating winding 44and the tripping coil 39, I provide manually operable trip button 45, areset button 49 provided with a sealing-in contactor 41 and a limitswitch comprising a switch arm 48 movable between the com tacts 49 and59 arranged to be actuated into engagement with the contact 49 by afinger 5i carried by the solenoid core 43, and into engagement with thecontact 59 by a finger 52 carried by the trip button 45. An overcenterspring 53 is provided for ensuring that the switch arm 48 will occupyone or the other of its extreme positions.

Assume now that the circuit breaker is in the reset position shown inFig. 4 and that it is desired to manually trip the circuit breaker. Inthis position the sealing-in contactor 41 is in circuit closingposition, the operating coil for the contactor being energized through acircuit which may be traced from the positive control bus 54 through thecontacts of the sealing-in contactor 41, the contacts of the trip button45, the conductor 55, the conductor 56 and the operating winding of thesealing-in contactor to the negative control bus 51. The finger 35 isheld in its latching position by the trip coil 39, the energizingcircuit therefor extending from the positive control bus 54 through thecontacts of the sealing-in contactor 41, the contacts of the trip button45, the conductors 55 and 56', the switch arm 48, the contact 49, theconductor 51', the trip coil 39 and the conductors 58 and 59 to thenegative control bus 51. Actuation of the trip button 45 opens theenergizing circuits for the sealing-in contactor 41 and the trip coil39, allowing the sealing-in contactor to open and the pivoted finger 35to move to its releasing position. At the same time, the finger 52 onthe trip button moves the switch arm 48 out of engagement with thecontact 49 and into engagement with the contact 58. The control circuitis now completely deenergizedand when the finger 35 moves out ofengagement with the latch 34, the carrier 29 is moved by the spring 36to trip the clrcuit'breaker. The respective positions of the circuitbreaker operating mechanism and the carrier 29 during the manualtripping operation is illustrated in Figs. "I and 8. In Fig. 7, thecircuit breaker is shown at an instant when, with the carrier movingtoward the left, the spring 29 has just moved over center relative tothe pivot point l4 and the pin 29 on the carrier has engaged the finger32 on the supporting arm l3. As the carrier 29 continues to move to theleft, the arm I3 is rotated about the pivot 54 and the toggle hinge 25begins to open against the force exerted by the spring 29. As soon asthe spring 29 moves overcenter relative to the hinge 25, however, theforce exerted thereby assists in breaking the toggle and the contact Inmoves to its open position with a snap action! position of the circuitbreaker at the end of the manual tripping operation is shown in Fig. 8.

Assume now that a is desired to reset the circuit breaker after thecircuit breaker has opened either in response to an abnormal steadyoverload or in response to a sudden rush of current. As the first stepin the resetting operation The' it is necessary to actuate the tripbutton to move the operating mechanism of the circuit breaker from theopen positions shown in either Fig. 5 or Fig 6 to the manually trippedposition shown in Fig. 9. As pointed out above, this actuation of thetrip button also serves to move the switch 49 into engagement with thecontact 59 to prepare an energizing circuit for the solenoid operatingwinding 44. Actuation of the reset button 46 will now complete anenergizing circuit for the operating winding 44 which may be traced fromthe positive control bus 54 through the contacts of the reset button 45,the contacts of the trip button 45, the conductors 55 and 5d, the switcharm 48, the contact 59, the operating winding 44 and the conductor 59 tothe negative control bus 51. A circuit is also completed through thereset button for energizing the sealing-in contactor 4'! which, whenclosed, lay-passes the reset button and maintains an energizing circuitfor itself and for the operating winding 44. Energization of theoperating winding 44 causes the solenoid plunger 43 to move quickly tothe right whereby the carrier 29 is moved to the extreme right-handposition shown in Fig. 9. As the carrier 29 moves to the right, the pin3| carried thereby engages the finger 32 and rotates the arm I3 aboutthe pivot M. Fig. 6 illustrates the position of the circuit breaker atthe instant that the pin 3| has just engaged the finger 32. Continuedmovement of the carrier to the right moves the spring 26 overcenterrelative to the hinge point 25 and the arms l3 and I3 move into straightline relation with a sna action. When the carrier reaches the extremeright-hand position, shown in Fig. 9, the spring .26 has movedovercenter relative to the pivot 54 and is effective to move the arms l3and I3 about the pivot to circuit closing position. When the plunger 43reaches its extreme right-hand position, the finger 5| carried therebymoves the switch arm 48 to 'deenergize the operating winding 44 andclose the energizing circuit for the trip coil 39. Upon deenergizationof the operating winding 44, the carrier 29 starts to move to the leftunder the force exerted by the spr ng 36 but is prevented from movingbeyond its reset position, shown in Fig. 4, by the latch fingers 34 and35, the pivoted finger 35 now being held in latching position by thetrip coil 39. In this position of the carrier 29 the spring 28 iseflective lightly to bias the circuit breaker contacts to the closedposition.

It will be evident now that I have provided a circuit breaker of verylight and simple construction which will permit high speed, tripfreeoperation in response to either abnormal substantially steady currentsor to a sudden rush of current and which may be manually tripped andreset as desired.

While I have shown a particular embodiment of my invention, it will beunderstood. of course. that I do not wish to be limited thereto sincemany modifications may be made. and I. therefore, contemplate by theappended claims to cover any such modifications as fall within the truespiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

l. A circuit breaker comprising a pair of reatively movable contacts, amovable conductor for actuating one of said contacts, said conductorbeing electrically connected in series with sa d contact, means forbiasing said conductor to close said contacts, electromagnetic means inserice with said contacts for establishing a magnetic field, a portionof said conductor being disposed in said magnetic field for applying tosaid closed contacts an additional closing bias proportional to theelectrodynamic reaction between said magnetic field and the current insaid conductor and means including said conductor portion and saidmagnetic field for opening said contacts upon the occurrence of apredetermined rate of change in the current.

2. A circuit breaker comprising a pair of relatively movable contacts, amovable conductor for supporting one of said contacts, said conductorbeing electrically connected in series with said contact, means forbiasing said conductor to contact closing position, electromagneticmeans in series with said contacts for establishing a magnetic field, aportion of said conductor being disposed in said magnetic field forapplying to said contacts a closing bias proportional to theelectrodynamic reaction between said magnetic field and the current insaid conductor portion, and conductor means connected with saidconductor portion to form a conductor-400p in said magnetic field foropening said contacts upon the occurrence of a predetermined rate ofincrease in the current.

3, A circuit breaker comprising a pair of relatively movable contactsnormally biased to circuit closing position, a movable conductor forsupporting one of said contacts, said conductor being electricallyconnected in series with said contact, means for establishing a magneticfield proportional to the current fiow through said contacts, a portionof said conductor being disposed in said magnetic field for applying tosaid closed contacts an additional bias, and shunt means connected tosaid portion of said conductor cooperating with said magnetic field toreverse the direction of current flow through said portion upon theoccurrence of a predetermined rate oi increase in the current throughsaid contacts whereby said conductor is moved to open said contacts.

4. A circuit breaker comprising a pair oi. relatively movable contactsnormally biased to circuit closing position, a movable conductor forsupporting one of said contacts, a magnetic blow-out coll adjacent saidcontacts in series therewith, means associated with said coil forestablishing a magnetic field when said contacts are closed, a portionof said movable conductor being disposed in said magnetic field forapplying to said closed contacts an additional closing bias and meansincluding said conductor and said magnetic field for opening saidcontacts upon the occurrence of a predetermined rate of increase in thecurrent.

5. A circuit breaker comprising a pair of relatively movable contactsnormally biased to closed circuit position, a. pivoted conductor bar forsupporting one of said contacts, electromagnetic means in series withsaid conductor and said contacts for establishing a magnetic field, aportion of said conductor being disposed in said magnetic field foroperation in one direction about said pivot when a substantially steadycurrent flows through said circuit breaker and means including saidconductor portion and said magnetic field for moving said conductorabout said pivot in another direction in response to'a predeterminedrate of increase in the current through said circuit breaker.

6. An electroresponsive device comprising a conductor-loop having amovable leg forming a side thereof, circuit connections Ior supplyingcurrent to said leg, and means for establishing a magnetic field throughsaid loop to move said leg in a predetermined direction upon the flow ofa substantially steady current through said loop, said loop and saidfield field being so related as to induce a reverse current in said legupon a predetermined rate of change of current in said leg to move saidleg in an opposite dlrection.

'7. A circuit breaker comprising a pair of relatively movable contacts,overcenter spring means for actuating one of said contacts between openand closed circuit positions, means for moving said spring meansovercenter to open said contacts, a trip-free means electrodynamicallyresponsive to a steady overload current for moving said one contact toopen circuit position, and means including said last mentioned meanselectrodynamically' responsive to a predetermined rate of increase incurrent for moving said contact to open circuit position.

8. A circuit breaker comprising a pair 01' relatively movable contactsnormally biased to closed circuit position, a pair of conductor armshinged together in endwise relation to form a toggle supportelectrically and mechanically connected to one or said contacts, saidsupport being pivotally mounted intermediate the ends of one of saidarms, means for establishing a magnetic field adjacent said armsproportional to the current in said circuit breaker, said arms beingdisposed in said field for moving said one contact about said hinge toopen circuit position in response to a predetermined value of currentthrough said circuit breaker, and means including said arms and saidfield for moving said one contact about said pivot to open circuitposition in response to a predetermined rate of change of current.

9. A circuit breaker comprising a pair of relatively movable contactsnormally biased to closed circuit position, a pair of conductor armshinged together in endwise relation to form a toggle supportelectrically and mechanically connected to one of said contacts, saidsupport being pivotally mounted intermediate the ends of one of saidarms, means for establishing a magnetic field adjacent said armsproportional to the current in said circuit breaker, said arms beingdisposed in said field for moving said one contact about said hinge toopen circuit position in response to a predetermined value of current.to one of said contacts, said support being pivotally mountedintermediate the ends or one of said arms, means for establishing amagnetic field adjacent said arms proportional to the current in saidcircuit breaker, said arms being disposed in said field for moving saidone contact about said hinge to open circuit position in response to a.predetermined value of current through said circm't breaker, and shuntmeans connected in parallel circuit relation with one of said arms. saidshunt means being disposed in said magnetic field to form a loop circuitincluding said one arm, said loop circuit and said magnetic fieldreacting upon a predetermined rate of increase of current to induce acirculating current in said loop of sufiicient magnitude to reverse thenormal flow of current through said one'arm, whereby said one contact ismoved about said pivot to open circuit position.

11. A circuit breaker comprising a pair of relatively movable contacts,a support for one of said contacts comprising a pair of conductor armshinged together in endwise relation to form a toggle electrically andmechanically connected to one of said contacts, said support beingpivotally mounted intermediate the ends of one of said arms, overcenterspring means having an end connected to one of said arms for normallybiasing said contacts to circuit closing position and for locking saidtoggle, means for moving the other end of said spring relative to saidcontact support to move said spring overcenter and open said contacts,electromagnetic means in series with said contacts disposed to reactelectrodynamically with a predetermined value of current in said arms tomove said contact about said hinge to open circuit position, and meansincluding said arms disposed to react electrodynamically with saidmagnetic field upon a predetermined rate of increase in current to movesaid one contact about said pivot to open circuit position.

PETER W. FORSBERG.

